Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 100005
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
705 PM EST TUE FEB 9 2016

.SYNOPSIS...
A BROAD AND MOIST AREA OF LOW PRESSURE WILL SLOWLY CROSS THE REGION
THROUGH WEDNESDAY NIGHT. CANADIAN HIGH PRESSURE WILL THEN BUILD IN
THURSDAY AND REMAIN THROUGH THE WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 645 PM...ANOTHER POTENT VORT MAX IS CURRENTLY ROUNDING THE
BASE OF THE DEEP LONG WAVE TROUGH...CROSSING THE CWFA THIS EVENING
AND PROVIDING SOME ENHANCEMENT TO RADAR RETURNS ACROSS THE REGION.
THE CAMS SEEM TO BE HANDLING THE SNOW SHOWER COVERAGE WELL...AND SO
WAS BLENDED INTO THE POP GRIDS WITH THIS UPDATE. EXPECT ISOLATED TO
SCATTERED SNOW SHOWERS ACROSS THE UPPER SAVANNAH VALLEY AND LOWER
PIEDMONT THIS EVENING...WITH A FEW FLURRIES ELSEWHERE EAST OF THE
MTNS. IN THE MTNS...ONGOING NWFS EVENT LOOKS ON TRACK...WITH
GENERALLY 1 INCH OR SO PER 3-6 HOUR RATES. HAZARDS IN PLACE LOOK ON
TRACK.

AS OF 230 PM EST TUESDAY...DEEP LONGWAVE H5 TROF CONTINUES TO
DOMINATE THE PATTERN ACROSS THE EAST/CENTRAL CONUS WITH A SERIES OF
SHORTWAVE IMPULSES SLIDING THROUGH THE BASE TONIGHT/OVERNIGHT BEFORE
THE ENTIRE AXIS LIFTS NORTHEAST ON WEDNESDAY.  AT THE SURFACE...A
RATHER SHARP PRESSURE GRADIENT IS PRESENT OVER NORTHEAST GA AND THE
WESTERN CAROLINAS THIS AFTERNOON TIED TO A LENGTHY LEE TROF ALONG
THE EASTERN SLOPES OF THE NC HIGH TERRAIN WHICH WILL CONTINUE
TO YIELD GUSTY WSW/WNW FLOW ALONG THE I85 CORRIDOR THROUGH THE
AFTERNOON HOURS.  IN ADDITION TO THE WINDS...WOULDNT BE SURPRISED
TO SEE A FEW FLURRIES OVER THE LAKELANDS REGION THROUGH THE NEXT
4-6 HOURS...HOWEVER NOT AMOUNTING TO MUCH AS MOISTURE WILL REMAIN
RATHER LIMITED BENEATH A SUPPORTIVE UPPER H5 IMPULSE.

MOIST WNW LLV FLOW WILL CONTINUE TO SLIDE OUT OF KY...THROUGH
TN...AND INTO WESTERN NC AND NORTHEAST GA TONIGHT YIELDING CONTINUED
UPSLOPE INDUCED SN SHOWERS OVER THE NC MTNS WITH THE GREATEST
CHANCES RESIDING ADJACENT TO THE NC/TN STATE LINE.  THIS PATTERN
WILL FINALLY START TO MODIFY INTO THE MID MORNING HOURS AS THE A
FORE MENTIONED UPPER TROF SHIFTS NORTHEAST ALLOWING FOR DIMINISHING
PRECIP CHANCES OVER THE SW NC MTNS AROUND MIDDAY...THEN FURTHER
NORTH THROUGH THE REMAINDER OF THE PERIOD.  GIVEN THAT LLV FLOW
REMAINS SOMEWHAT BACKED AND ALSO THE FACT THAT THERE REALLY IS
NO SIGNIFICANT GREAT LAKES CONNECTION FOR MOISTURE...THINK SNOW
TOTALS WILL CONTINUE TO REMAIN BELOW 24 HOUR WARNING CRITERIA.
THUS...WILL CONTINUE WITH CURRENT WWY...AND WCY GIVEN WINDS REMAIN
ELEVATED ABOVE 3500FT AMIDST COLD ADVECTIVE FLOW...THROUGH 6AM ON
WEDNESDAY...WITH FURTHER EXTENSION BEING A POSSIBILITY OVERNIGHT
TONIGHT IF WARRANTED BY 00Z GUIDANCE.  NEW SNOW TOTALS THROUGH
6AM LOOK TO RANGE IN 2-3 INCH RANGE ACROSS THE SMOKIES...WITH 1-2
INCHES FAVORED FURTHER NORTH...WITH A TRACE POSSIBLE EASTWARD ALONG
THE ESCARPMENT.  OTHERWISE...EXPECTING DOWNSLOPING FLOW TO PREVAIL
ACROSS THE LOW TERRAIN ON WEDNESDAY ALLOWING FOR PARTLY CLOUDY
SKIES AND SLIGHTLY WARMER TEMPERATURES WITH HIGHS TOPPING OUT NEAR
THE 40 DEGREE MARK.  WNW WINDS WILL BE QUITE GUSTY OVER MUCH OF
THE NC/SC PIEDMONT REGION AS WELL AS NORTHEAST GA TOMORROW WITH
GUSTS IN THE 25-30MPH RANGE BEING A POSSIBILITY.  THIS COMBINED
WITH RH VALUES IN THE LOWER/MID 20S COULD PRESENT INCREASED FIRE
DANGERS...THUS STATEMENTS MAY BE ISSUED LATER THIS EVENING FOR
SUCH AFTER COLLABORATION WITH LAND MANAGERS IS CONCLUDED.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 220 PM TUESDAY...NW FLOW SNOW EVENT WILL BE ALL BUT DONE BY
THE BEGINNING OF THE SHORT TERM PERIOD...AS MOISTURE QUICKLY BECOMES
TOO SHALLOW TO SUPPORT SHOWER GENERATION. HOWEVER...SNOW SHOWERS MAY
MAKE AN ENCORE APPEARANCE AROUND DAYBREAK THU...AS MOISTURE DEEPENS
BRIEFLY SOUTH OF THE UPPER JET AXIS.

THE MAIN EARLY SHORT TERM CONCERN WILL BE THE CONTINUED POTENTIAL
FOR LOW WIND CHILL ACROSS THE MOUNTAINS WED NIGHT. BASED UPON THE
EXPECTED WIND MAGNITUDE AND TEMPERATURE REGIME...EXPECT ADVISORY
CRITERIA TO EXIST ACROSS A LARGE ENOUGH AREA TO WARRANT AN ADVISORY
FOR ALL OF THE NORTHERN MTNS...BUT JUST FOR THE HIGH ELEVATIONS
ACROSS THE SOUTHERN AND CENTRAL MOUNTAINS. WINDS WILL LIKELY BE
HOWLING IN THE HIGH ELEVATIONS WED NIGHT...AS H8 WINDS INCREASE TO
40-50 KTS. IN FACT...THE HIGH PEAKS AND RIDGE TOPS MAY SEE GUSTS TO
60 MPH DURING THIS TIME. HOWEVER...NEUTRAL ADVECTION AND A
RELATIVELY WEAK SURFACE GRADIENT SHOULD PRECLUDE THIS STRONGER FLOW
FROM FILTERING INTO THE VALLEYS.

FRIDAY...GUIDANCE DIGS ANOTHER SHORT WAVE INTO THE BASE OF THE MEAN
TROUGH ACROSS THE EASTERN CONUS. WHILE ALL THE MODELS REFLECT SOME
WEAK SURFACE DEVELOPMENT IN RESPONSE TO THIS FEATURE...WHERE THIS
OCCURS IS THE MATTER OF SOME CONTENTION. IN FACT...THE NAM IS FAR
ENOUGH NORTH WITH ITS SURFACE WAVE THAT IT SPREADS LIGHT PRECIP
ACROSS MUCH OF THE FORECAST AREA DURING THE MORNING.
INTERESTINGLY...EARLIER RUNS OF THE ECMWF LOOKED QUITE SIMILAR TO
THIS...BUT THE LATEST RUNS HAVE BACKED OFF ALMOST COMPLETELY FROM
THIS SCENARIO. NONE OF THE OTHER DETERMINISTIC GUIDANCE IS ON BOARD
WITH THE NAM...AND ENSEMBLE OUTPUT INDICATES THIS WETTER SOLUTION IS
AN OUTLIER. NEVERTHELESS...THERE/S ENOUGH OF A SIGNAL TO HOLD ON TO
SLIGHT CHANCE POPS...MAINLY ACROSS THE SOUTHEAST ZONES...AND ACROSS
THE NW...WHERE SOME NORTHWEST FLOW SNOW SHOWERS WILL BE POSSIBLE
LATE IN THE DAY. IF PRECIP DOES DEVELOP...AND DEVELOPS EARLY ENOUGH
IN THE DAY...SNOW WILL BE POSSIBLE IN THE PIEDMONT...BUT AGAIN THIS
IS A LOW PROBABILITY OF A LOW QPF EVENT.

TEMPS WILL MODERATE DURING THE SHORT TERM...BUT STILL REMAIN A GOOD
10-12 DEGREES BELOW NORMAL UNDER THE ANOMALOUSLY DEEP TROUGH.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 220 PM EST TUESDAY...FORECAST CONFIDENCE IS RELATIVELY HIGH
FOR THE EARLY PART OF THE EXTENDED...THE WEEKEND...BUT RATHER LOW
FOR EARLY NEXT WEEK. A WESTERN RIDGE/EASTERN TROUGH PATTERN WILL BE
IN PLACE AT THE START OF THE PERIOD FRIDAY NIGHT. DEEP LAYER
NORTHWESTERLY FLOW WILL CONTINUE ON THE BACK SIDE OF THE EASTERN
TROUGH AXIS INTO THE SOUTHERN APPALACHIANS FRIDAY NIGHT THROUGH
SATURDAY...WITH ASSOCIATED UPSLOPE MOISTURE SLOWLY DIMINISHING.
ANTICIPATE AT LEAST ISOLATED TO SCATTERED UPSLOPE SNOW SHOWERS
CONTINUING IN THE NORTHERN MOUNTAINS THROUGH FRIDAY NIGHT WITH 850
MB TEMPERATURES DOWN NEAR MINUS 10 C OR SO.

HEIGHTS WILL THEN RISE GRADUALLY FROM THE WEST OVER THE
WEEKEND...WITH A SHORTWAVE RIDGE CROSSING THE FORECAST AREA ON
SUNDAY. MEANWHILE...AN INTENSE ARCTIC HIGH PRESSURE REGION WILL
SETTLE IN ALONG THE EASTERN SEABOARD. THE BEST OVERLAP OF LINGERING
NW FLOW GRADIENT AND THE ONSET OF THE ARCTIC AIR WILL BE SATURDAY
NIGHT. PLENTY OF SUB ZERO WIND CHILLS ARE LIKELY IN THE NC MOUNTAINS
EARLY SUNDAY MORNING...WITH MINUS 10 TO MINUS 20 VALUES LIKELY IN
THE NORTHERN MOUNTAINS. TEMPERATURES WILL THEN LIKELY BE 15 TO 25
DEGREES BELOW CLIMO BY SUNDAY WITH MANY AREAS STRUGGLING TO GET
ABOVE FREEZING DURING THE DAY.

UNCERTAINTY INCREASES IN THE FORECAST SUNDAY NIGHT INTO MONDAY AS AN
UPSTREAM TROUGH AMPLIFIES ACROSS THE MIDWEST...BUT WITH MODEL
DIFFERENCES SHOWING UP AS THE BASE OF TROUGH REACHES THE SOUTHEAST.
WARM FRONTAL MOISTURE MAY BRUSH THE SOUTHERN APPALACHIANS AHEAD OF
THIS SYSTEM LATE SUNDAY...BUT THE BEST MOISTURE AND FORCING AHEAD OF
A REINFORCING COLD FRONT WILL BE LATER SUNDAY NIGHT THROUGH MONDAY
NIGHT. THE GFS/GEFS FEATURE A MORE PROGRESSIVE TROUGH PASSAGE INTO
TUESDAY WHLE THE ECMWF REAMPLIFIES THE WAVE WEST OF THE
APPALACHIANS. THIS PERMITS ANOTHER ROUND OF SOUTHEAST MOISTURE TO
DEVELOP. THERMAL PROFILES SUGGEST AN ONSET AS SNOW THROUGH GIVEN THE
COLD AND DRY ANTECEDENT AIR SUNDAY NIGHT INTO MONDAY. SOME
CHANGEOVER TO RAIN ACROSS SE SECTIONS WILL BE POSSIBLE MONDAY
AFTERNOON BEFORE A RETURN TO SNOW PROFILES INTO TUESDAY WITH ANY
LINGERING OR REDEVELOPING PRECIPITATION. UNCERTAINTY REMAINS TOO
HIGH ON TIMING AND QPF...HOWEVER...FOR ANY HWO MENTION AT PRESENT.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...VFR THROUGH THE PERIOD.  BASED ON THE LATEST RADAR AND
HIGH RESOLUTION MODEL GUIDANCE TRENDS...STILL EXPECT NOTHING MORE
THAN PERHAPS A BRIEF FLURRY THIS EVENING. OTHERWISE...LOW VFR
STRATOCUMULUS WILL PERSIST INTO THE OVERNIGHT HOURS. WINDS SHOULD BE
LOSING THEIR GUSTINESS AROUND 00Z...BUT REMAIN IN THE 7-10 KT RANGE
OUT OF THE WNW. GUIDANCE AGREES THAT THE WINDS WILL BACK TO WSW DUE
TO WEAK LEE TROFFING IN THE LEE OF THE BLUE RIDGE BEFORE DAYBREAK.
THEN THE WINDS WILL INCREASE YET AGAIN AFTER DAYBREAK OUT OF THE WNW
WITH LOW END GUSTS. THERE WILL BE LESS LLVL MOISTURE ON
WEDNESDAY...BUT STILL ENOUGH FOR SCT-BKN LOW VFR CLOUDS BY THE AFTN.

AT KAVL...MODERATE NORTHWEST FLOW ALONG THE TN LINE WILL CONTINUE
TO YIELD SHSN THROUGH MUCH OF THE TAF CYCLE.  FLIGHT CATEGORIES
SHOULD REMAIN AT LOW VFR LEVELS WITH OVC STRATUS PREVAILING. BACKED
WINDS WILL KEEP GUSTS SOMEWHAT INTERMITTENT THRU THE OVERNIGHT...BUT
THEN FLOW VEERS TO MORE DUE NW WEDNESDAY AFTN...ALLOWING FOR MORE
GUSTS. CLOUDS SHOULD START TO GRADUALLY SCATTER OUT AS MOISTURE
DECREASES WEDNESDAY AFTN.

ELSEWHERE EAST OF THE MTNS...SIMILAR TO THAT OF KCLT ABOVE WITH
FLURRIES BEING POSSIBLE AT ALL SC SITES...WITH A BRIEF SHOT AT A
SHSN AT KAND THIS EVENING. OTHERWISE LOW VFR CIGS WILL PREVAIL
THROUGH THE EVENING HOURS ATOP GUSTY WSW/WNW FLOW...BEFORE GUSTS
SUBSIDE AFTER MIDNIGHT...THEN INCREASE YET AGAIN BY LATE MORNING.

OUTLOOK...A DEEP UPPER TROF WILL BEGIN TO LIFT NE OUT OF THE
AREA...TAPERING OFF THE NW FLOW SNOW SHOWERS AND CLEARING SKIES.
ANOTHER DISTURBANCE WILL QUICKLY CROSS THE AREA ON FRIDAY...WHICH
MAY PRODUCE A BRIEF PERIOD OF WINTRY PRECIP ACROSS THE AREA.

CONFIDENCE TABLE...

            00-06Z        06-12Z        12-18Z        18-00Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  99%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...WINTER WEATHER ADVISORY UNTIL 6 AM EST WEDNESDAY FOR GAZ010.
NC...WINTER WEATHER ADVISORY UNTIL 6 AM EST WEDNESDAY FOR NCZ033-
     048>053-058-059-062-063.
     WIND CHILL ADVISORY UNTIL NOON EST WEDNESDAY FOR NCZ033-
     048>052-058-059-062>064.
     WIND CHILL ADVISORY FROM 7 PM WEDNESDAY TO 10 AM EST THURSDAY
     FOR NCZ033-048>052-058-059-062>064.
SC...NONE.

&&

$$
SYNOPSIS...SBK
NEAR TERM...ARK/CDG
SHORT TERM...JDL
LONG TERM...HG
AVIATION...ARK


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